MacDingbats (Zapf Dingbats) is a character encoding used on classic Mac OS. Actually, it's more of a font than an encoding, though in the era when it was first used the distinctions between character encodings, character sets, and fonts were much fuzzier than they are now. As an encoding, it's a peculiar one, since it offers no way of encoding normal letters with which one might write text in any language, unless it's a peculiar language that has "letters" resembling things like airplanes and telephones. (An alternative-music magazine in the 1990s did reportedly publish an article entirely in this font/encoding, according to the Wikipedia article.) The only way it was actually usable was via the clumsy way character encodings and fonts were actually implemented on old-school computers like the early Macs; they let you write text in normal ASCII, MacRoman, or other reasonable encodings, and set the font of parts of it to something wildly different like Zapf Dingbats and have it magically show up in the characters at the same code position in that font, allowing the use of symbols that had no place in any standardized character set.
In the modern era, however, those Dingbats characters have been inducted officially into Unicode, mostly in the "Dingbats" section starting at code position 2700 hex. (A few are placed elsewhere, and a few of the positions in the Unicode Dingbats range are given to different dingbat-like characters.)
See Macintosh encodings for related encodings.